The AM3A Accident Range Noble Gas Monitor is designed to measure high range noble gas activity on a continuous basis. Included with the AM3A are parallel particulate/iodine collectors for retention of high activity levels of particulates and iodine. The P/I filters are lead shielded to reduce ALARA concerns and include active gamma monitoring of the accumulated does rate. A gamma GM detector (model GG1W) is associated with each P/I filter to measure the accumulated dose rate on the filter media. Once the sample gases have passed through the parallel collectors, the noble gas activity level is measured in a lead shielded sample volume. The GG1W detector is located within the lead shield and inserted into the sensitive volume for measurement. The output from the detector communicates with the skid mounted display and control unit (model RM1R) using Ethernet (TCP/IP), RS232, or RS485 communications for display of the measured activity and for alarm determination. The noble gas sampler includes a vacuum transducer to automatically correct the measured activity to standard pressure. Local RM1R display and control units are included for system operation, data concentration and communication. The vacuum pumping system uses a positive displacement metal bellows pump for transport of sample gases through the monitoring system. A mass flow meter and proportional control valve allows the sample flow rate to be either manually set to the desired flow or to match the sample flow rate to a stack or vent velocity for representative sampling

A flow rate signal is provided to the local RM1R electronics for determination of total release and for calculation of concentrations. Alarms are included for annunciation of a low flow condition. The AM3A operates in conjunction with the Apantec model(s) AM3F or AM3M normal range skid to provide seamless monitoring over the entire range. Upon increasing activity measured by the AM3M/F normal range monitor, the accident range AM3A monitor will automatically start the sample pump and begin monitoring. Once the activity level drops, the AM3M/F will automatically begin normal range monitoring and the AM3A accident level monitor will stop monitoring activities. The AM3A samples at a significantly lower sample flow rate to reduce the build up of high radioactivity on the particulate and iodine filters.

GG1W Gamma GM Detector The GG1W Intelligent Gamma Probe is an integrated real-time Gamma radiation-monitoring device that provides highly accurate indication of ambient Gamma radiation over a wide range. The GG1W uses a pair of halogen quenched Geiger Mueller tubes for sensitivity to ambient gamma radiation levels. The GM tubes are operated using a “Time-To-Count” method which removes the limitations associated with traditional ‘constant bias’ GM tube circuits.

The GG1W is housed in a rugged cylindrical aluminum housing with a NEMA4 rating. When provided with an internal check source, the detector is designated as Model GG1WC.